DC SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES WITH BISRCACUO BICRYSTAL GRAIN-BOUNDARY JUNCTIONS AT 77K

We have developed de superconducting quantum interference devices (SQU IDs) with grain boundary junctions of a BiSrCaCuO (BSCCO) thin film on a SrTiO3 (100) bicrystal substrate with a misorientation angle of 36. 8 degrees. The T-c and J(c) of the BSCCO film were 93 K and 3 x 10(5) A/cm(2) at 77 K, respectively. These SQUIDs operated at 77 K. The I-V characteristics of the SQUIDs were of resistively shunted junction (RS J) type. A SQUID with 20-mu m-wide junctions showed Fraunhofer-like Bu r-voltage characteristics. The I(0)R(n) product and the modulation vol tage of a SQUID with 10-mu m-wide junctions were 23 mu V and 6 mu V at 77 K, respectively. The flux noise measured in a flux-locked loop mod e was 2.0 x 10(-5)Phi(0)/Hz(0.5) in the white noise region.